Signaling system



Jan. 12 1926. 1,569,003

A. M. CURTIS SIGNALING SYSTEM Filed Jan. 21, 1922 2 Sheets-Sheet 1 i FILTER 1 .1 1% i FILTER c: c: c cc;

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Jan. 12 1926.

1,559,003 A. M. CURTIS SIGNALING SYSTEM piled Jan 21, 1922 2 Sheets-Sheet 2 //7 uen for: 1405* fen M Cuff/l5. W azg/ Patented den. 12, 1926.

UNHTED STATES PATENT OFFICE.

AUSTEN M. CURTES, OF EAST ORANGE, NEE? JERSEY, AESIGNOR TO WESTERN ELEC- TRIO COIEPANY,

YORK.

INCORPORATED, OF NE'W YORK, N. Y., A CORPORATION OF NEW SIGNALING SYSTEM.

Application filed January 21, 1922.

To all whom it may concern:

Be it known that I, AUs'rnN M. CURTIS, a citizen of the United States of America, residing at East Orange, in the county of Essex, State of New Jersey, have invented cer tain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a signaling sys tem and more particularly to a high speed telegraph system.

Telegraph transmitters as at present constituted generally involve electrical. contacts adapted to be closed either mechanically, as in the Wheatstone transmitter, or electrically, by means of relays associated with the transmitter. These contacts almost always chatter, that is, rebound several times after striking, with the result that the signal period is shortened and the wave form of the transmitted signal impulses is distorted by the partial closing due to this chatter. fit ordinary speeds this is not troublesome, but as the speed increases the time of chatter becomes more nearly equal to the. duration of the signal period and transmission becomes almost impossible.

The present invention is directed to a telegraph transmitter which operates with-.

out chatter and hence is free from the disadvantages noted above.

The primary object of the invention is to provide a high speed telegraph transmitter which does not involve moving contacts. Another object is the provision of control means for supplying signal impulses of predetermined duration to a telegraph transmission circuit. Still another object is to provide means for supplying signal impulses of undistorted wave form to the transmission circuit of a telegraph system. A feature of this invention is a condenser having a movable element which auto1nati cally controls the properties of the condenser dielectric.

According to this invention an oscillator is provided comprising an electric discharge device having its input and output circuit coupled in feed back relation and including a tuned circuit adapted to determine the frequency of the oscillations generated. The tuned circuit in addition to the usual inductance and capacity includes a pair of opposed Serial No. 530,762.

conducting surfaces connected to the opposite terminals of the main capacity element between which a perforated tape is adapted to be fed as in the well-known Nheatstone transmitter. The perforated tape is of dielectric material and hence by its cooperation with the conducting surfaces constitutes an auxiliary condenser the capacity value of which depends upon whether a perforated or lmperforate section of the tape lies between the conducting surfaces. As the tape is caused to traverse the space between the conducting surfaces the constants of the tuned circuit will be changed each time an imperforate tape section is replaced by a per forated section and vice versa. Thus, when an imperforate tape section intervenes between the conducting surfaces, oscillations of one frequency will be generated by the os cillator and when a perforated section lies between these surfaces, oscillations of a different frequency will be produced. Throughout the following descriptions these two frequencies will be designated the normal and changed frequencies, respectively.

As contemplated by the present invention the change of frequency of the oscillations supplied by the generator is utilized to control the supply of signaling current to a transmission circuit. The application of this control mechanism to Morse, carrier current and radio systems will be hereinafter de scribed.

Briefly described the output circuit of the oscillator is connected to the input circuit of an electric discharge relay device through a selective circuit adapted to discriminate between the normal and changed frequencies, to thereby control the flow of current in the output circuit of the relay.

For signal purposes the rectifying prop erties of the discharge device may be utilized to produce unidirectional impulses in its output circuit and these rectified impulses may be transmitted to a distant re ceiving station over a Morse line or they may be used to control the supply of carrier waves to a transmission circuit for communication over a carrier current line or between radio stations.

Again, the relay device may operate as a repeater and the low frequency current flowlOO ing in its output circuit may be transmitted over a line or cable, or may be used to modulate a carrier wave, the modulated wave being transmitted over a carrier line or radiated from the antenna of a radio station. i hen the relay device is used to rectify the current supplied by the oscillator, the selective means connecting the output circuit of the oscillator with the input circuit of the relay, may be designed to transmit with minimui'n attenuation either the non mal or changed frequency depending upon the type of system with which it is used. For example, the normal frequency may be impressed upon the control element of the rectifying device to polarize it and thereby reduce the space current to Zero. In this case the selective means will be designed to pass current of normal frequency but to impose a high impedance to the current of the changed frequency. The blocking potential will therefore be normally impressed upon the control element or grid of the device and its space current will be re duced to zero, whereas, when a changed frequency current is supplied by the oscillator the grid potential will be reduced to Zero and hence a current impulse will flow through the output circuit of the device and be impressed upon the transmission circuit. In the second case the selected means will be resonant for the changed frequency. The normal frequency will be suppressed, the potential of the grid will be zero and current will be continuously supplied to the transmission circuit or line from the output circuit of the device, whereas, when a current of changed frequency is supplied by the oscillator it will be transmitted through the selective means to block the rectifier and thereby reduce its space current to zero. The former will be hereinafter referred to as the transmission method of control and the later will be designated the suppression method.

The operation of this invention and its various parts will be clear from the follow ing description read in conjunction'with the attached drawing in which Fig. 1 shows the invention applied to a low frequency stem. Figs. 2 and 2 show the perforated tape and conducting surfaces; Fig. 8 shows the invention used for supplyin modulating current to acarrier wave system; Fig. 4 illustrates a radio system involving the invention; Fig. 5 shows a circuit arrangement for producing beat frequency control 1 the control mechanism is shown applied to a low frequency telegraph system in which current impulses of difilerent polarities are transmitted over a line to actuate a receiving de ice at a distant station. This arrangement may operate on the principle of the well-known Baudot system or the impulses of different polarities may be used to identify dots and dashes of the Morse code.

its shown in this figure the control mechanism comprises the two oscillators 1, 1 of the type shown and described in U. S. Patent 1,356,763, issued October 26, 1920, to B. V. L. Hartley having their output circuits separately coupled by transformers T to the input circuits of balanced rectifiers through selective means 3 and 3, which may be tuned circuits or filters.

Connected in parallel with the capacity element of the frequency determining circuits l and f associated with the respective oscillators l and l" are two pairs of juxtaposed conducting surfaces 5 and 5 between which a tape 6 is adapted to be fed in the well-known manner. The tape 6 is preferably of dielectric material and may be either an ordinary li hcatstone tape or one specially treated to increase its dielectric properties. Conducting surfaces 5 and 5 and the inter veuing tape 6 constitute a pair of auxiliary capacity elements which, as described above, are included in the frequency determining circuits of the respective oscillators 1 and 1.. It is noted that a metallic perforated tape may also be used in place of the dielectric tape to constitute with the conductive surfaces 5 and 5 the auxiliary capacity element associated with the respective oscillators.

As the tape 6 is fed bet-ween the conductive surfaces 5 and 5 associated 'with the oscillatory circuits 4 and 4; respectively, their tuning will be varied. Hence, the frequency of the current generated and, due to the selective action of the means 3 and 3, the voltages impressed upon the input cir cuits ofthe device 2 or 2 will be changed whenever a perforated section replaces animperforatescction between the juxtaposed surfaces 5 and as the case may be.

As shown in Fig. 2, a perforation lies between the surfaces 5 associated with the device 1 and an oscillating current of changed frequency will, therefore, be impressed upon the selective means In passing it may be stated that, while the surfaces 5 and tape perforation are shown circular, it may be preferable under certain conditions to use perf rations and conductire surfaces of other forms.

Let it be assumed that the suppression method defined above is being used. In this case the space current of the device 2 is normally Zu'o, because of the polarizing potential im ressed upon 3 control cle u nicnt by the oscillator 1 nd no current is supplied to the line. However, when a perforation lies between the surfaces 5 as shown in this figure, and since the circuit 3 imposes a high impedance to the current of changed frequency, the potential impressed upon the control element of the device 2 will be reduced substantially to zero. Current will therefore flow from the battery 7, through the resistance 8 and across the space within the device 2. The drop of potential across the resistance 8 being impressed between the line 9 and ground 10, and the device E2 being blocked, an impulse will be transmitted to the distant station due to this potential. Fiii'nilarly, when a perforation intervenes between the surfaces 5, an imperforate section of the tape being between the opposed surfaces 5, the tuning of the oscillatory circuit 4. and hence the frequency of the current supplied by the oscillater 1 will be changed and the potential impressed upon the control element of device 2 will be reduced substantially to Zero. A drop of potential will occur across resist ance 8 but of opposite sign relatively to line and ground and a current impulse of oppo site polarity will therefore be transn'iitted over the line 9. lVith this method of operation, the perforations of the tape are of uniform size and hence the time period of the impulses transmitted over the line will be equal.

In Fig. 2 there is shown a section of tape provided with a single row of perfora tions which are of different longitudinal dimensions. This tape is designed to control a single oscillator and may be associated, for example, with either pair of the conducting surfaces 5 or 5 shown in Fig. 1 to control the frequency of the current supplied by the oscillator with which the pair of conducting surfaces is associated. Current impulses of one polarity, but of unequal duration will be supplied to the line 9 and the operation of a Morse key will be thereby simulated. A tape of this kind is used with the arrangements shown in Figs. 3, at and 5.

As shown in Fig. 3, the oscillating cur rent transmitted through the selective means or tuned circuit 3 is impressed upon the input circuit of the modulator 12 by the transformer or repeating coil 11. The secondary of the transformer 11 may be shunted by a condenser to constitute a circuit tuned to the frequency of the modulating current. Obviously, a capacity coupling can be used to supply the modulating current to the input circuit of the modulator in place of the transformer 11. In this circuit he selective device 3 will be designed to transmit current of the changed frequency whereby the carrier wave supplied by the source 13, which is also coupled to the input circuit of the modulator may be modulated. The modulated wave is transferred by the transformer 14 with or without amplificiu tion to the transmission circuit, which may be an antenna 15 for radio communication or the line 16 of a carrier current system.

Instead of using the current supplied by the controlled oscillator to modulate a can rier wave in the manner described with reference to Fig. 3, it may be utilized to control a carrier wave source as shown in F f. In this figure, two methods of using the control currents for carrier transmission are shown.

In one arrangement the oscillating current transmitted through the selective circuit 3 is impressed upon the control element of the device 2 to control the space current and hence the flow of unidirectional current in the output circuit of the device which includes a resistance 17. A movable contact 18, associated with the resistance 17, may be adjusted to determine the energy supplied to the source of carrier waves 19 which is adapted to be thereby controlled to impress waves of carrier frequency upon the line or antenna 20 by means of a transformer.

According to the second method, the controlled oscillator 1 will be designed to sup ply a wave of carrier frequency. By moving switch 11 to its alternative position the secondary of the transformer 11 will be in cluded in the antenna circuit which is grounded at 11 by adjusting the switch 11. The antenna will be tuned to discriminate between the normal and changed frequencies. If the transmission method of control is used, a train of high frequency waves will be supplied to the transmission circuit only when a perforated portion of the tape lies between the conducting surfaces 5 associated with the controlled oscillator. If the suppression method is employed a carrier. wave will be transmitted continuously and a signal impulse will be identified by the suppression of the carrier wave.

In practice, it may be found that the difference between the normal and changed frequencies is too small to admit of selection by a tuned circuit or filter, in which case the circuit shown in F ig. 5 may be used. As therein shown the controlled oscillator 21 normally generates an alternating current of high frequency, for example, one million cycles and the source supplies alternating current of the same frequency. These alternating currents are impressed upon the input circuit of the detector 2; the output circuit of which includes the resonant circuit or filter designed to pass a current. of relatively low frequency. Normally. since the controlled oscillator 21 and the source 22 supply currents of the same frequency to the detector 3, no current will be transmitted through the low pass filter ever, when current of changed fre is supplied by the controlled source, due to the presence of a perforation between the conducting surfaces 5, as described above, an alternating current of the difference frequency will be impressed upon the filter 24. If this filter is selective of the difference frequency, which in the case of the ordinary tape and a given example of discharge de vice, will be of the order of 2000 cycles, current of relatively large amplitude will fiow through the filter 2%. and will be available at its terminals 25.

The beat frequency current may be rectified to control the supply of signals to a Horse line as described above. The beat frequency current may be used as described in connection with Fig. 3 to control the supply of modulating current to the input circuit of a modulator, or it may be used as described in Fig. 4 to control the supply of carrier waves to a transmission circuit.

An arrangement for using control currents of beat frequency for controlling unidirectional signal impulses of both polarities is shown in Fig. 6. In this figure, instead of using separate sources associated with each of the controlled oscillators for producing the beat frequency currents impressed upon the two selective means, the

controlled oscillators themselves employed to produce control currents of different beat frequencies. The circuit shows two control oscillators 30 and 31 of the type l'iereinbefore described which normally gencrate oscillations of the same frequency. The

constants of the frequency determining circuit of the oscillator 30 are different from those of the oscillatory circuit of oscillator 31 and consequently, the changed frequency of oscillator 30, when a perforation lies between the conducting surfaces 5, will be different from the changed frequency of 31 when a perforation intervenes between the surfaces 5. By arranging the perforations in the tape so that an imperforate section lies between one pair of conducting surfaces when a perforated section intervenes between the other pair of conducting surfaces, the frequency of the current supplied by one oscillator will always be normal when that supplied by the other is changed. Hence, when the conducting surfaces 5 are opposite a perforation the frequency of the beat frequency current resulting from detection will be different from that produced when a perroration intervenes between the surfaces 5.

The alternating current paths of the oscillators and 31 are coupled to the input circuit of the detector 32, the output circuit of which includes the selective circuits or filters 33 and 3 1, the output terminals of which are respectively connected to the input circuits of the rectifying devices 5 O and 3G. The output circuits of devices 3 and 36, including resistances 37 and 38, respectively, are connected in balanced relation to a common source.

One terminal of resistance 37 is connected to the line 39 and one terminal of resistance 38 remote from the source is grounded at 40. Grid leak paths, each constituted by a high resistance shunted by a condenser, are included in the control or input circuits of the rectifiers and 36. Filter 33 is de signed to pass the beat frequency wave when the oscillator 30 is supplying changed frequency oscillations and filter 34 transmits the beat frequency when the oscillator 31 is supplying changed frequency oscillations.

Normally no charge is impressed on the grid of either of the devices 35 or 36 and hence oppositely directed space currents of substantially equal amplitude flow through the resistances 37 and 38. These resistances being of equal magnitude, no potential difference occurs between the line 39 and ground 0. When a perforation lies between the conducting surfaces 5 of oscillator 30 and the beat frequency wave produced by detection is transmitted through the filter 33 to the grid of relay 35, the current flowing through the resistance 37 in cluded in the output circuit of the detector is substantially zero. However, since normal current flows through the resistance 38 included in the output circuit of the relay 36, a potential difference is produced between the line and ground and hence a signal impulse will be impressed upon the line for transmission to a distant station. In a similar manner, an impulse of the reverse polarity will be transmitted over the line 39 when the frequency of the current supplied by the oscillator 31 is changed.

Obviously, by employing two pairs of oscillators in the manner shown in Fig. 5 to produce different beat frequencies and impressing these different frequency currents upon the selective devices 33 and 34, the relay devices and 36 may be controlled to supply signal impulses of opposite polarities to the line 39. Again, by impressing negative polarizing potentials upon the grid elements of the devices 35 and 36 to reduce their normal space currents to zero and employing beat frequency currents, produced either by two oscillators as described with reference to Fig. 6 or two pairs of oscillators as shown in Fig. 5, to counteract the effect of these potentials wholly or in part, the transmission method of control may be used to supply signal impulses of opposite polarities to the line.

As shown in Fig. 6 either of the arrangements described with reference to Figures 1, 5 or 6 may be utilized for high speed signal transmission over a cable. In this case any one of the arrangements previously described for supplying currents of different frequencies may be used. The currents of different frequencies are supplied to the terminals T, and are transmitted through the selective circuits i1 and 42 and a transformer 43 to a cable 44:. The different frequency alternating currents will then be supplied under the control of the tape and the selective circuits ll and 4-2, to the cable at the transmission station and, at the receiving station, these different frequency currents will be seected by tuned circuits or filters. The selected currents may be utilized in any well known manner to control the operation of a receiver, recording device, or to transmit signal impulses over associated land lines. for example, at the receiving station the incoming signal currents of different frequencies may be rectified in a manner similar to that described in Figs. 1 and 6 to supply signal impulses of opposite polarities to a land line.

IVhile in the preceding description, the tape controlled oscillator is illustrated as of the type described in the above mentioned Hartley patent, it will be apparent that any other type of oscillator may be used in place thereof. Thus, an oscillator including a de vice which depends for its operation upon positive ionization or an oscillator having a tuned frequency determining circuit included in the input or output circuit of a discharge device may be substituted for the Hartley type oscillator referred to above. Again, any well-known type of modulator, detector, or rectifier may be used in a circuit arrangement which involves the characteristic features of this invention. Furthermore, while several signaling systems embodying the invention have been described with the object of setting forth some of the various modes of applying it for communication purposes it is emphasized that the use of the invention is not so limited, since it may be applied to any signaling system adapted to employ its principles. From the preceding remarks it will be appreciated and it is to be understood that this invention is not limited to the specific details and arrangements herein set forth but only by the scope of the appended claims.

What is claimed is:

1. A. signal transmission system comprising an oscillation generator, a transmission circuit, a message carrying medium having portions of different dielectric properties, and means actuating said medium whereby said portions control the generator to determine the signal supplied to the transmis sion circuit.

2. In a signal transmission system, the combination of an oscillation generator, means upon which a message is recorded having portions of different dielectric properties, and means whereby the frequency of the oscillation supplied by said generator is controlled by the varying dielectric properties of said means.

3. In a signal transmission system the combination of an oscillation generator, an oscillating current circuit therefor provided with a variable capacity element including means upon which a message is recorded for varying the capacity value of said element.

4: In a signal transmission system the combination of an oscillation generator, an oscillating current circuit therefor provided with a capacity comprising conductive elements and a dielectric element upon which a message is recorded.

5. In a signal transmission system the combination of an oscillation generator, an oscillating current circuit therefor provided with a capacity element including a medium upon which a message is recorded, whereby the dielectric properties of said medium are varied.

6. A signal transmission system comprising a transmission circuit, an oscillation generator, a message carrying medium having portions of different dielectric properties, said portions controlling the frequency of the oscillations supplied by said generator, and selective means coupled to said generator for controlling the supply of signal cur rent to said transmission circuit.

7. In a signal transmission system, the combination of an oscillation generator, an oscillating current circuit therefor including a capacity comprising conductive surfaces and associated therewith, for varying the value of said capacity, a dielectric element upon which a message is recorded.

8. In a signaling system, the combination of an oscillation generator, an oscillating circuit therefor including a capacity, means having portions of different dielectric prop crties, and means whereby the value of said capacity is controlled by the different dielectric properties of said other means.

9. In a signal transmission system, the combination of an oscillation generator, an oscillating current circuit therefor, a message carrying means having portions of different dielectric properties, and means whereby said portions control the frequency determining elements of said oscillating current circuit.

10. A signal transmission system comprising an oscillation generator an oscillating current circuit therefor having a ca pacity comprising conductive surfaces and a varying dielectric message carrying medium between said surfaces.

11. A signal transmission system comprising a transmission circuit, an oscillation generator, a message carrying means having portions of different dielectric properties, the frequency of said generator being controlled by the portions of said means, and

means for controlling the supply to said circuit of the current generated by said oscillator.

12. A signal transmission circuit comprising an oscillation generator, a message carrying means having portions of different dielectric properties, means whereby the frequency of the oscillations supplied by said generator, is controlled by said portions, and selective means for selectively suppressing certain of the oscillations generated and transmitting other oscillations to energize said transmission circuit.

13. A signal transmission system comprising a transmission circuit, an oscillation generator, an oscillating current circuit therefor provided with a capacity including amessage carrying medium for varying the value of said capacity, and means to control the supply of current to said transmission circuit due to the change in said capacity.

14".. A signal transmission system comprising a transmission circuit, an oscillation generator, an oscillating current circuit therefor provided with a capacity including a message carrying medium of varying dielectric properties, and selective means for controlling the supply of current from said generator to said transmission circuit.

15. A signal transmissionsystem comprising a transmission circuit, an oscillation generator, an oscillating current circuit therefor including conductive surfaces and a perforated tape therebetween constituting a variable condenser for changing the tuning of said oscillating current circuit, and means to control the supply of current to said transmission circuit which is responsive to the change of tuning.

16. A radio transmission system comprising an antenna, a source of radio frequency waves coupled to said antenna, means upon which a message is recorded to vary the dielectric properties thereof, means whereby the frequency of the waves produced by said source is controlled by the varying dielectric properties of said means for controlling the supply of signal currents to said an tenna. v v

17 A radio transmission system comprising an antenna, a generator of radio frequency waves including a frequency determining circuit coupled to said antenna, and

a message carrying medium constituting at least a portion of an element included in said circuit for changing the constants of said frequency determining circuit to control the supply of signal waves to said antenna.

18. A radio transmission system comprising an antenna, an oscillator for generating adio frequency waves comprising an electric discharge device having an anode, a. cathode and a grid, coupled input and out-- put circuits associated with said device and including a frequency determining circuit, means for coupling said oscillator to said antenna, and a message carrying means of varying dielectric properties, means where by the constants of said frequency dctcr nining circuit are controlled by the varying dielectric properties of said message carrying means to control the supply of signal waves to said antenna.

19. A variable condenser comprising conductive surfaces, and means for controlling the dielectric properties of the space between said surfaces.

20. A variable condenser comprising conductive surfaces, and means for automatically controlling the dielectric properties of the space between said surfaces.

21. A variable condenser comprising conductive surfaces, and an intervening element movable relatively to said surfaces, said element having varying dielectric properties.

22. A variable condenser comprising conductive surfaces, and an intervening strip of dielectric material movable relatively to said surfaces, different portions of said strip having different dielectric properties.

23. A variable condenser comprising conductive surfaces, and an intervening strip of dielectric material. movable relatively to said surfaces, successive portions of said strip having different dielectric properties.

Zt. A variable condenser comprising conductive surfaces, and an intervening strip of dielectric material movable relatively to said surfaces, successive portions of said In witness whereof, I hereunto subscribe my name this 20th day of January A. 1)., 1922.

AUSTEN M. CURTIS. 

